Electronic musical instrument

ABSTRACT

An electronic organ usable for educational purposes includes a first tone generating circuit for generating the equal tempered musical scale and a second programmable tone generating circuit for simultaneously generating a second musical scale such as a Just, Pythagorean, mean tone or other scale. Separate keyboards are provided to allow a direct comparison of the tonal characteristics of the various scales. The programmable tone generating circuit utilizes programmable digital dividers with switchable feedback taps to allow the generating circuit to be rapidly tuned to any desired scale.

United States Patent [151 Maynard .Iune 28, 1974 ELECTRONIC MUSICAL INSTRUWNT [75] Inventor: I i-ed B. Maynard, Phoenix, Ariz.

[73] Assignee: Motorola lino, Franklin Park, Ill.

[22] Filed: Nov. 115, 11972 [21] Appl. No.1 306,639

[52] US. Cl. 84/11.]17, 84/101 [51] Int. Cl. Gltlh 3/06 [58] Field of Search .1 84/101, 1.23, 1.17, 1.24, 84/].03; 328/39 [56] References Cited UNITED STATES PATENTS 3,236,931 2/1966. Freeman 84/123 3,287,648 11/1966 Poole 328/39 X 3,288,909 11/1966 Volodin; 84/l.0l X

3,509,454 4/1970 Gossel 84/l.01 X

3,546,355 12/1970 Maynard 3,601,518 8/1971 Hill 3,617,901 11/1971 Franssen 84/101 Primary Examiner-Stephen J. Tomsky Assistant Examiner-U. Weldon Attorney, Agent, or Firm-EugeneA. Parsons; Vincent J. Rauner [57] ABSTRACT An electronic organ usable for educational purposes includes a first tone generating circuit for generating the equal tempered musical scale and a second programmable tone generating circuit for simultaneously generating a second musical scale such as a Just, Pythagorean, mean tone or other scale. Separate keyboards are provided to allow a direct comparison of the tonal characteristics of the various scales. The programmable tone generating circuit utilizes programmable digital dividers with switchable feedback taps to allow the generating circuit to be rapidly tuned to any desired scale.

5 Claims, 2 Drawing Figures MASTER PROGRAMMA8LE Q}; RELATIONSH/P a/v/oms 7a 2a ocravz DIV/BEES I I oar/1V5 all/mews l 66 LEADS 66 LEADS f 66 A5405 I I v 1 I mass KEY SW/TCHES COUPLl/VG IrE) sw/rcme's SWITCH v 66 LEADS PMEWEJma 19M D/V/DERS HAV/A/G 4 REL AT/O/VSH/P 66 LEADS KEY SW/TCHES sum 1 OF 2 MASTER OSCILLATOR /2 /4 BUFFER 7 PROGRAMMABLE PROGRAM 0/V/0ER5 0cm v5 p/v/afRs 24 ENE/m5 66 LEADS COUPL/A/G KEY snare/v55 SW/TCH 66 LEADS 2 ELECTRONIC MUSICAL INSTRUMENT BACKGROUND 1. Field of Invention This invention relates generally to musical instruments, and more particularly to electronic musical instruments of the keyboard type which may be readily tuned to several musical scales, including the equal tempered scale and various primitive and non-standard scales. The instrument may be tuned to two different scales simultaneously to allow a direct comparison to be made between the tonal characteristics of the various tunings.

2. Prior Art There are many applications wherein it is necessary to provide a musical instrument that can be tuned to various tuning systems other than the equal tempered scale. Such instruments are useful for educational purposes to illustrate the differences between modern and ancient tuning, and for musical experimentation with non-standard tuning schemes.

Several techniques for tuning a musical instrument to musical scales other than the equal tempered scale are known, however, all such techniques require that each note of the scale be individually tuned to the proper frequency.

Whereas this technique provides a way to tune an instrument to a non-standard musical scale, the tuning procedure is very complex and time consuming. Trained personnel employing special equipment are required, and the tuning process often requires several hours, thereby precluding the possibility of a direct comparison of the tonal qualities of different scales.

SUMMARY It is an object of the present invention to provide an electronic musical instrument that is readily tunable to a variety of musical scales with a minimum of time and effort.

It is a further object of this invention to provide a musical instrument that can be simultaneously tuned to two different musical scales to provide a direct comparison of the tonal qualities of various musical scales.

It is another object of this invention to provide a musical instrument that can be quickly and repeatably tuned to any experimental scale, including a twentyfour note quarter tone scale, without the use of special equipment or trained personnel.

In accordance with a preferred embodiment of the invention, a master oscillator, which may be a crystal controlled oscillator for stability reaons, is used to provide a reference signal to a pair of frequency generating circuits. A 3.58 MHz color television crystal may be used for reasons of economy. The first frequency generating circuit utilizes twelve divider chains having divisor numbers (numbers by which the input frequency is divided) selected to generate twelve signals having frequencies related by the twelfth root of two for generating the equal tempered musical scale from the frequency provided by the master oscillator. The second frequency generating circuit also includes twelve divider chains, at least eleven of which are programmable. The divider chains employ digital dividers having switchable feedback taps for allowing the divisor numbers to be set to any desired value. By adjusting the feedback taps, the ratio of the divisor numbers of the various divider chains can be selected to generate any desired musical scale, including ancient and experimental scales. A twenty-four note quarter tone scale may be generated by tuning the second frequency generating circuit to produce tones having frequencies lying between the frequencies produced by the first frequency generating circuit. The musical scales generated by the two frequency generating circuits are applied to separate keyboards to allow simultaneous sounding of tones of different scales for comparison thereof. The instrument can be readily tuned to different scales by simply changing the feedback taps on the digital dividers by means of a program card, jumper wires or switches on the panel of the instrument.

DESCRIPTION OF Til-IE DRAWINGS In the drawings:

FIG. l is a block diagram of the musical instrument according to the invention; and

FIG. 2 is a block diagram of the divider chains within the programmable divider of FIG. ll, portions thereof broken away.

DETAILED DESCRIPTION Referring to FIG. l, a master oscillator lltlt having a frequency control resistor 12 connected thereto is connected to the input of a buffer amplifier M. The outputs of the buffer amplifier 114 are connected to fixed and programmable tone generating divider means, in this embodiment, divider circuits l6 and 26, respectively, each of which has twelve outputs. The twelve outputs of the tone generating divider circuits l6 and 26 are connected to octave dividers l8 and 28, respectively. The octave dividers each have sixty-six outputs, in this embodiment, which are connected to keyboards 20 and 30, respectively. The outputs of the keyboards 20 and 30, which can be coupled together by means of a cross coupling switch 24 to allow two scales to be simultaneously sounded from a single keyboard, are connected through an adder circuit 32 to an amplifier 34 which has an output connected to a loudspeaker 36. A divider control program 22 is connected to the tone generating circuit 26.

In operation, oscillations from the master oscillator 10 are applied to the buffer 14, which in turn applies the oscillations to the tone generating divider circuits I6 and 26. The tone generating divider circuit 16 includes twelve divider chains having divisor numbers related to each other by the twelfth root of two for generating twelve output signals having frequencies related to each other by the twelfth root of two. The aforementioned twelve output signals define one octave of an equal tempered musical scale, however, other divisor number relationships may be used to generate other musical scales. Other octaves are generated by the 0ctave divider 18 which divides the frequencies of each of the twelve signals applied thereto by numbers related to each other by 2, 4i, 8, etc. The octave divider 18 provides output signals having frequencies related to the twelve signals provided by the generating divider 16, but offset one or more octaves therefrom. In this embodiment, the octave divider 18 provides 66 output signals to give a range of five and one half octaves. It should be noted, that although the octave divider 16 has 66 outputs in this embodiment, any number may be used, depending upon the frequency range of the instrument, and still fall within the scope of the invention.

The 66 output signals from the octave divider 18 are applied to the keyboard 20. The keyboard 20 has sixtysix keyswitches for passing the signals corresponding to any depressed keys to the adder 32. Each keyswitch controls a gate, which may include a mechanical or an electronic switch, connected in series with one of the 66 output leads from the octave divider 18 and the lead to the adder 32 for passing signals from divider 18 to the adder 32. The coupling switch 24 parallels corresponding keyswitches of the two keyboards to allow both scales to be simultaneously sounded from a single keyboard. In another embodiment, one of the keyboards may utilize double pole keyswitches, one of the poles of each keyswitch being connected to one of the outputs of octave divider 18 and the other to divider 28 to simultaneously pass signals from both dividers. A single pole switch connected in series with one group of poles and the adder 32 can be used to restore independent operation. The adder 32 passes the signal from the keyswitches 20 to an amplifier 34 for amplification thereby, and subsequent reproduction by the loudspeaker 36. 4

The operation of the second tone generating divider circuit 26 is similar to the operation of the tone generating divider circuit 16 except that the divisor numbers of the dividers within the generating divider circuit 26 are variable by means of the program 22. The programmable dividers in the tone generating divider circuit 26 are shown in FIG. 2, and will be described farther on in the specification.

The programmable divider circuit 26 provides twelve output signals to another octave divider 28, similar to the octave divider 18. The octave divider 28 provides 66 output signals which are applied to the keyboard 30, which is similar to the keyboard 20. The signals passed through the keyboard 30 are applied to the adder 32 for combination with the signals from the keyboard 20 and subsequent application to the amplifier 34 and loudspeaker 36. The adder 32, the amplifier 34 and the loudspeaker 36 serve as a reproducing means for the signals from the keyboards 20 and 30.

Referring to FIG. 2, two divider chains 40 and 60, and a partial drawing of a twelfth divider chain 100 similar to chain 60 of the programmable tone generating divider circuit 26 are shown. The first divider chain 40 comprises eleven divide by two circuits or binary dividers 41-51 which are connected to each other to form a binary counter. A feedback network for setting the chain to a predetermined count comprises a capacitor 52 connected to the output of the divider 51 and to a which is 53 whichis connected to set terminals of the dividers 41-47 and 49. Although a particular feedback circuit is described in this embodiment, it should be noted that any feedback system that provides the desired count may be employed and still fall within the scope of the invention. The divider chain 60 has eleven divide by two circuits or binary dividers 61-71 connected to each other to form a binary counter. A capacitor 72 is connected to the output of the divider 71 and to a feedback line 73. The feedback line 73 is connected to set terminals of the dividers 61-71 by means of eleven program switches 81-91, respectively. The divide by two dividers used in the divider chains 40 and 60 are well known flip flops or bistables commonly used in digital dividers, and may be built in discrete or integrated circuit form. Although the divider chains 40 and 60 employ binary dividers connected as binary counters to accomplish the division, ring counters or shift registers may also be used. In addition, other divider chains (not shown) similar to the divider chain 61) are used to provide a total of twelve divider chains for generating twelve musically related frequencies.

The divider chain 40 is pre-programmed to divide by a predetermined divisor number, however, a programmable chain similar to the divider chain 60 may be used. The divisor number is determined by the interconnections of the line 53 and the various divider stages. The specific interconnections are selected as in the following discussion of the operation of the divider 60.

The divisor number of the divider chain 60, and hence the position of the switches 81-91 is determined by the frequency of the master oscillator 10 of F IG. 1 and the musical scale to be programmed. For purposes of explanation, let us assume that the Pythagorean scale is to be programmed, and that the divider chain 60 will produce the C sharp note of that scale. Let us further assume that the frequency of the master oscillator 10 is such that the oscillation frequency thereof must be divided by a divisor number of 1601 in order to provide an output frequency at an output point 74 that is proportional to the Pythagorean C sharp.

The divider chain 60 has eleven stages and the maximum count or divisor number thereof is 2, or 2048. Hence, if all of the divide by two dividers 61-71 are set to a 0 state, a 1 will be provided by the output divider 71 after 2048 pulses have been applied to the input of the divider 61, and division by 2048 will have been achieved. If division by a number lower than 2048 is desired, a number corresponding to the difference between 2048 and the desired divisor must be preprogrammed into the divider chain 60. In the current example, the divisor number required to generate a Pythagorean C sharp is 1601, and the number 447, which is equal to the difference between 2048 and 1601 must be programmed into the divider. With the 447 programmed into the divider, only 1601 additional pulses need be applied to the input of the divider 61 to provide an output pulse from the divider 71, and division by 1601 is achieved.

Since the divider chain 60 employs divide by two or binary counters, the number 447 must be converted to binary form in order to preset the divider chain to that number. The number 447 converted to binary from is 00110111111. This number can be pre-programmed into the divider chain 60 by closing the switches 81-86, which correspond to the ls in the 1s through 32s places of the binary number 001 101 l l 1 l 1, and switches 88 and 89, which correspond to the 1s in the 128s and 256s places of the binary number, respectively. Hence, each time a 1 appears at the output of the divider 71, the aforementioned I is applied to the dividers 61-66 and dividers 68, 69 through the switches 81-86 and switches 88, 89, respectively, to preset the chain to 447, and division by 1601 is achieved. In a similar fashion, any number less than 2048 and greater than 1024 may be preset into the divider chain 60 by determining the binary form of the desired number and by closing the switches corresponding to the ls of the binary number. The other divider chains (not shown) are programmed in a similar manner. and any musical scale can be synthesized by closing the necessary switches to generate the desired frequency for each note of the scale. The dividing technique employed in the divider chains is known as an up counting technique, however, a down counting technique wherein a number related to the divisor number is programmed into the divider chain and the count is subsequently reduced to zero, or other dividing techniques may be used and still fall within the scope of the invention.

The switches fill-S ll, which form the program for the divider 6t), and analogous switches for the other divider chains (not shown) correspond to the program 22 of FIG. ll. Although these are shown schematically as single pole switches in FIG. 2, any interconnection means between the capacitor 72 and the various dividers, such as, for example, switches, jumper wires or electronic switches may be used and still fall within the scope of the invention. The instrument of the preferred embodiment utilizes panel switches to provide maximum flexibility of programming, but pre-programmed program cards using jumper wires mounted thereon to achieve rapid programming of predetermined scales may also be used.

I claim: 11. A tone generating system for a musical instrument including in combination:

tone generating divider means for simultaneously providing twelve first signal frequencies having a predetermined frequency relationship therebetween corresponding to a complete equal tempered vmusical scale to twelve output junctions thereof in response to a reference frequency signal applied to an input junction thereof, said tone generating divider means including twelve frequency divider chains, each divider chain having a predetermined divisor number and an output coupled to one of said output junctions, the relationship between the divisor numbers of said divider chains corresponding to the frequency relationship between said twelve first signal frequencies; programmable tone generating divider means for simultaneously providing twelve second signal frequencies having a predetermined frequency relationship therebetween corresponding to one of a plurality of complete musical scales to twelve output junctions thereof in response to a reference frequency signal applied to an input junction thereof, said programmable tone generating divider means including twelve variable frequency divider chains at least eleven of said variable frequency divider chains having variable divisor numbers, each divider chain having an output coupled to one of said output junctions, the divisor number of one of said divider chains being related to the divisor number of a second one of said divider chains by a factor of two, the divisor number of each of the other ones of said divider chains being adjustable and related to the divisor number of said second one of said chains by a factor greater than one and less than two; program means for independently changing the frequency relationship of one of said signal frequencies with respect to any other of said signal frequencies connected to said variable frequency divider chains for changing the divisor numbers of individual chains to change the frequency relationship between said twelve second signal frequencies to determine the one of said musical scales to be provided by said programmable tone generating divider means;

a source of electrical oscillations connected to the input junctions of said tone generating divider means and said programmable tone generating divider means for applying the reference frequency signal to said frequency divider chains and to said variable frequency divider chains a first octave divider connected to said tone generating divider means for simultaneously generating at least twelve first octave related signals in response to said twelve first signal frequencies, each of said first octave related signals having a frequency that is related to one of said twelve first signal frequencies by an integral multiple of two;

a second octave divider connected to said programmable tone generating divider means for simultaneously generating at least twelve second octave related signals in response to said twelve second signal frequencies, each of said second octave related signals having a frequency that is related to one of said twelve second signal frequencies by an integral multiple of two;

reproducing means for receiving and reproducing signals applied thereto;

a first keyboard having at least twelve first keyswitches coupled to said first octave divider for receiving said twelve first octave related signals, said twelve first octave related signals having a predetermined frequency relationship therebetween corresponding to a complete equal tempered musical scale, each first keyswitch being coupled to said reproducing means for selectively applying only a predetermined single one of said first octave related signals to said reproducing means upon actuation thereof, said first keyswitches being manually playable singly and in predetermined combinations to produce musical melodies in the equal tempered scale; and

a second keyboard having at least twelve second keyswitches coupled to said second octave divider for receiving said twelve second octave related signals, one of said second octave related signals having a frequency related to the frequency of a second one of said second octave related signals by a factor of two, the frequencies of the other ones of said octave related signals being lower than the frequency of said one of said second octave related signals and higher than said second one of said second octave related signals, each second keyswitch being coupled to said reproducing means for selectively applying only a predetermined single one of said second octave related signals to said reproducing means upon actuation thereof, said second keyswitches being manually playable singly and in predetermined combinations to produce musical melodies in theone of said musical scales provided by said programmable tone generating divider means determined by said program means.

2. The combination recited in claim ll wherein said frequency divider chains and said variable frequency divider chains each include a plurality of binary dividers connected to each other to form a binary counter.

3. The combination recited in claim 2 wherein said tone generating divider means and said programmable tone generating divider means each include twelve divider chains for providing twelve musically related signal frequencies.

3 8 2 1 ,460 7 8 4. The combination recited in claim 2 wherein each the chain. of said variable frequency divider chains includes leed- 5 The combination recited in claim 4 wherein Said gq means conneqed i the Output and to binary interconnection means includes a plurality of switches, dividers of the chain, said feedback means having variable interconnection means for selectively connecting 5 each swltch bemg Connected to one of said binary the output of the chain and to predetermined binary dividersviders thereof for determining the divisor number of 

1. A tonE generating system for a musical instrument including in combination: tone generating divider means for simultaneously providing twelve first signal frequencies having a predetermined frequency relationship therebetween corresponding to a complete equal tempered musical scale to twelve output junctions thereof in response to a reference frequency signal applied to an input junction thereof, said tone generating divider means including twelve frequency divider chains, each divider chain having a predetermined divisor number and an output coupled to one of said output junctions, the relationship between the divisor numbers of said divider chains corresponding to the frequency relationship between said twelve first signal frequencies; programmable tone generating divider means for simultaneously providing twelve second signal frequencies having a predetermined frequency relationship therebetween corresponding to one of a plurality of complete musical scales to twelve output junctions thereof in response to a reference frequency signal applied to an input junction thereof, said programmable tone generating divider means including twelve variable frequency divider chains at least eleven of said variable frequency divider chains having variable divisor numbers, each divider chain having an output coupled to one of said output junctions, the divisor number of one of said divider chains being related to the divisor number of a second one of said divider chains by a factor of two, the divisor number of each of the other ones of said divider chains being adjustable and related to the divisor number of said second one of said chains by a factor greater than one and less than two; program means for independently changing the frequency relationship of one of said signal frequencies with respect to any other of said signal frequencies connected to said variable frequency divider chains for changing the divisor numbers of individual chains to change the frequency relationship between said twelve second signal frequencies to determine the one of said musical scales to be provided by said programmable tone generating divider means; a source of electrical oscillations connected to the input junctions of said tone generating divider means and said programmable tone generating divider means for applying the reference frequency signal to said frequency divider chains and to said variable frequency divider chains a first octave divider connected to said tone generating divider means for simultaneously generating at least twelve first octave related signals in response to said twelve first signal frequencies, each of said first octave related signals having a frequency that is related to one of said twelve first signal frequencies by an integral multiple of two; a second octave divider connected to said programmable tone generating divider means for simultaneously generating at least twelve second octave related signals in response to said twelve second signal frequencies, each of said second octave related signals having a frequency that is related to one of said twelve second signal frequencies by an integral multiple of two; reproducing means for receiving and reproducing signals applied thereto; a first keyboard having at least twelve first keyswitches coupled to said first octave divider for receiving said twelve first octave related signals, said twelve first octave related signals having a predetermined frequency relationship therebetween corresponding to a complete equal tempered musical scale, each first keyswitch being coupled to said reproducing means for selectively applying only a predetermined single one of said first octave related signals to said reproducing means upon actuation thereof, said first keyswitches being manually playable singly and in predetermined combinations to produce musical melodies in the equal tempered scale; and a second keyboard having at least twelve second keyswitches coupled to said second octave divider for receiving said twelve second octave related signals, one of said second octave related signals having a frequency related to the frequency of a second one of said second octave related signals by a factor of two, the frequencies of the other ones of said octave related signals being lower than the frequency of said one of said second octave related signals and higher than said second one of said second octave related signals, each second keyswitch being coupled to said reproducing means for selectively applying only a predetermined single one of said second octave related signals to said reproducing means upon actuation thereof, said second keyswitches being manually playable singly and in predetermined combinations to produce musical melodies in the one of said musical scales provided by said programmable tone generating divider means determined by said program means.
 2. The combination recited in claim 1 wherein said frequency divider chains and said variable frequency divider chains each include a plurality of binary dividers connected to each other to form a binary counter.
 3. The combination recited in claim 2 wherein said tone generating divider means and said programmable tone generating divider means each include twelve divider chains for providing twelve musically related signal frequencies.
 4. The combination recited in claim 2 wherein each of said variable frequency divider chains includes feedback means connected to the output and to the binary dividers of the chain, said feedback means having variable interconnection means for selectively connecting the output of the chain and to predetermined binary dividers thereof for determining the divisor number of the chain.
 5. The combination recited in claim 4 wherein said interconnection means includes a plurality of switches, each switch being connected to one of said binary dividers. 